Note: Descriptions are shown in the official language in which they were submitted.
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DISCLOSURE OF THE INVENTION
Technical Field
The present invention relates to a mobile
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electromedical apparatus for Intraoperative RadioTherapy
(or "IORT") by means of an electron Linear Accelerator
(or "linac").
Background Art
An electron linac is an evacuated waveguide in which
a high-frequency travelling electromagnetic wave is
excited, the axial electric field of which accelerates
electrons. The phase velocity of the wave is made equal
to the velocity of electrons by assembling irises in the
guide, which delimitate accelerating coupled resonant
cavities. The linac is supplied by a radiofrequency (or
"RF") oscillator, particularly a cavity magnetron,
through a guiding structure or means (any structure or
means being meant, by such an expression, fit for guiding
electromagnetic waves, e.g. rectangular or circular
waveguides, and coaxial cables). A feature of a linac is
the collimation of the beam, i.e. the parallelism of the
trajectories of the electrons it emits.
A mobile "linac for IORT" is a mobile apparatus for
applying radiations to produce a destructive effect on a
tumour tissue. Electron irradiation has the advantage
relative to photon irradiation of penetrating in the
tumour tissue in a modulated manner (according to the
desired depth), with the exclusion of surrounding healthy
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tissues. The surgeon after the removal of a tumour fixes
the area to be treated with the radiotherapist and
selects the energy of the beam with the sanitary
physicist to administer the proper dose at a set depth.
A known-art apparatus includes a mobile radiating
head, or shortly "head", containing an irradiation group
including a linac. The beam emitted by this one is
collimated by means of an applicator and scattered
through the interaction with air existing inside the
applicator. The applicator includes an upper applicator,
directly connected with the radiating head, and a lower
applicator, which is arranged in the surgical breach.
With the object in view of the treatment, the upper
applicator, in an operating stage of docking (i.e. of
aligning and coupling) is brought in axis with the lower
applicator, at a short distance from it, and connected to
it through a ring nut.
The radiating head is supported by a"stand",
including an articulated arm assembled on a motor mobile
bedplate by a coupling which allows its yaw and pitch.
The radiating head is assembled to the arm by a coupling
which allows its roll and pitch.
In known-art apparatuses the irradiation assembly is
assembled in the radiating head, and the RF generator
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assembly is assembled in the arm of the stand, separately
from the radiating head, beyond the coupling of this one.
The waveguide that connects the linac to the RF generator
assembly is a flexible waveguide that steps over the
coupling of the radiating head, passing outside the
apparatus, and which in operation bends and twists,
correspondingly assuming bending and twisting
configurations.
Problems are connected with such an external
flexible waveguide, which are overcome by the mobile
radiotherapy linac forming the subject-matter of
unpublished European Patent Application EP06425479,
having the title "Internal-Waveguide Mobile Linac for
Radiation Therapy", filed on 10th July, 2006, in the name
of the same Applicant of the present application.
Document EP06425479 relates to an electromedical
apparatus for intraoperative radiation therapy by means
of an electron linear accelerator, including an arm
including means for generating electromagnetic waves,
which arm supports a radiating head including means for
linear acceleration of electrons, connected with the
means for generating electromagnetic waves through
guiding means, and for such an apparatus it teaches a
fabricating solution according to which the guiding means
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include two waveguide tracts reciprocally connected
through a rotary coupling, a waveguide tract of which,
that passes between the head and the arm, being a
flexible waveguide. In this way the external waveguide is
substituted with an internal waveguide.
Disclosure of the Invention
With the solution taught in Document EP06425479,
however, there is still a flexible waveguide present,
which restrictions are connected to. Indeed, it is
subject to a wear rate, and it determines a limit to the
freedom of pitch angular range of the radiating head
within +45 .
Moreover, the present invention takes its steps from
ascertaining that the knowledge is important of the
angular position of the head in space (with respect to a
reference) - which also depends on the product of its
pitch and roll rotations (with respect to the same
reference) - in the progress of its operation, with the
object of the docking manoeuvre and for a correct
positioning of a radioprotection element, said the "beam
absorber", under the operating bed. The beam absorber,
typically composed of a lead cubic block having a
thickness of 15 cm, it is necessary to absorb the "hard"
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energy-loss radiation, or Brehmsstrahlung, emitted by the
electrons of the beam, at the output of the linac,
passing through the body of the patient. Indeed, this
radiation is dangerous for the persons who are in or pass
through the places below the operating room. The beam
absorber is to be centred on the electron beam at the
output of the linac, the position whereof is also
determined by the roll and pitch rotations. On the
contrary, the deformations the flexible guide undergoes
in its operation do not allow a precise measurement of
the pitch angular position of the radiating head.
Moreover the aforesaid knowledge is useful to
remotely verify the good working status of the apparatus,
which can be tested by checking the right response of it
to commands.
Therefore, it is the object of this invention to
provide an internal-waveguide linac for IORT wherein the
aforesaid flexible waveguide and the restrictions
connected thereto are removed; particularly, wherein the
radiating head has a pitch angular range of +90 ; and
wherein the pitch angle of the radiating head turns out
to be precisely measured, so that the angular position
thereof, as results also from the roll and pitch
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rotations thereof, and, consequently, the direction in
space of the electron beam at the output of the linac
assembled in the head turn out to be precisely
computable.
Such an object is reached according to this
invention by providing that a linac apparatus for IORT
includes, in combination, a first rotary coupling and a
second rotary coupling, which support the radiating head
of the apparatus on the arm of the stand respectively
movable in roll and pitch; and that the guiding means for
supplying the linac include three mechanically separate
tracts, whereof an extreme tract of output from the means
for generating electromagnetic waves and an extreme tract
of input to the electron linear acceleration means, and
an intermediate tract therebetween, that connects them,
with the heads whereof the extreme tracts are
respectively put in electric continuity through the first
and the second coupling. Thus all the guiding means, no
more subjected to any deformation in the progress of the
rotations of the radiating head, can be rigid waveguides,
and the object of the present invention is reached.
The second rotary coupling when rotating can provide
the measure of the pitch angle of the radiating head.
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The present invention envisages that means are
provided for sensing the respective, pitch and roll,
angular positions of the movable portions of the two
rotary couplings, e.g. an encoder in correspondence with
each one. The sensed values provided by such means can
thus be provided to computing means, in functional
communication therewith, fit for computing, based on such
roll and pitch, the angular position of the electron beam
and all the data connected therewith for the docking
manoeuvres and the positioning of the beam absorber. The
computing means can provide these values to display means
for an operator or to an automatic control system of the
apparatus.
Therefore, it is the subject-matter of this
invention an electromedical apparatus for intraoperative
radiation therapy by means of an electron linear
accelerator according to annexed independent Claim 1.
Preferred embodiments are set forth in dependent Claims.
Brief Description of Figures in the Drawings
The present invention will be fully understood based
on the following detailed disclosure of a preferred
embodiment thereof, only given as a matter of example,
absolutely not of restriction, referring to the annexed
drawing, wherein:
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- FIGURE 1 represents a perspective view of a linac
for IORT according to the present invention.
Best Mode for Carrying Out the Invention
Articulated arm A is represented in FIGURE lof a
linac apparatus for IORT, comprising at a first extremity
thereof a housing 1 intended to contain a high-voltage
power-supply and a RF generator assembly including an
oscillator, e.g. a cavity magnetron or a klystron. At a
second extremity, opposite the first one, arm A supports
a radiating head 2 including an electron linac 20,
endowed with an output diaphragm 20' of the electron beam
emitted by the linac.
Arm A is assembled through an arm coupling 3 which
supports it in pitch motion, on a link (not represented)
built for being assembled in yaw motion on a motor mobile
bedplate (not represented) . The coupling of arm 3 finds
itself in an intermediate position between housing 1 and
radiating head 2.
Radiating head 2 is mechanically assembled onto
articulated arm A by means of the combination of a first
and of a second rotary coupling. First rotary coupling ,
or roll coupling 4 includes a fixed portion 41, integral
with arm A, and a mobile portion 42. Second rotary
coupling, or pitch coupling 5, preceptive, includes a
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fixed portion 51 integral with mobile portion 42 of roll
coupling 4, and a mobile portion 52 assembled integral
with linac 20. The rotation axis of pitch coupling 5 can
be perpendicular to the rotation axis of roll coupling 4.
Radiating head 2 is supported by a pivoting 63
having its rotation axis coaxial with the one of second
coupling 5 and engaged by a gearwheel 22 through which
the pitch motion thereof is actuated.
The electromagnetic waves at the output of the RF
oscillator are transferred to linac 20 through a
waveguide assembly 6, including three mechanically
separate tracts, of which an extreme one 61 at the output
of the oscillator and an extreme one 62 at the input of
the linac (through an insertion rigid waveguide stub 23),
connected through an intermediate tract 63, with the
heads whereof they are respectively put in electric
continuity through first and second rotary couplings 4
and 5.
The aforementioned combination of dual rotary
coupling and three-tract waveguide assembly, apparently
will allow the rotations in both rolling and pitching of
the head, without deformation of the waveguide tracts.
So, all these ones can be formed of rigid waveguides.
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It is envisaged that encoders, or other means (not
illustrated) are provided for sensing the respective,
pitch and roll, angular positions of the mobile portions
of the two rotary couplings, in correspondence with each
one of them, in conjunction with a circuit board or other
computing means, in functional connection with the
encoders, fit for computing the position of the electron
beam at the output of the linac, also based on such pitch
and roll positions. Means for sensing the angular
positions and circuit boards fit for the aforementioned
object fall within the skill of the average man of the
art and therefore will not be described herein.
The present invention has been described and
illustrated referring to a preferred embodiment thereof,
but it is to be expressly understood that variations,
additions or omissions can be made thereto, without
departing from the relevant scope of protection, which
only remains restricted by the annexed claims.
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